The invention concerns a shell cap of plastic material having a front convex portion which transitions into a cylindrical portion and which is provided with depressions which are arranged in radiating form and which end in the cylindrical portion. A peripheral groove crossing the depressions is formed at the transition between the convex and the cylindrical portions.
A bullet or shell cap of that kind is known, for example, from FR 2 762 385 A. The convex portion of the shell cap is comparatively stable because upon impact it causes deployment of the cylindrical portion. However, it has now been found that, in soft target medium conditions, the impact impulse is too slight to cause that shell cap to burst in spite of the weakening depressions in the longitudinal direction and the peripheral groove.
The object of the invention is to avoid those difficulties, and this object is achieved by providing at least one additional peripheral groove in the convex portion.
The peripheral grooves which cross the radiating depressions in a right-angled relationship subdivide a large region of the shell cap into areas, between which there are only thin-wall connecting strips. The increased number of desired-fracture locations provided by this arrangement substantially improves the bursting characteristics of the shell cap. In addition, the depressions and grooves facilitate penetration of the soft target medium between the non-weakened areas of the shell cap. Therefore, the spin of the shell generates tangential forces which additionally assist in causing the shell cap to break open.
Preferably the peripheral grooves are deeper than the depressions arranged in a radiating form. The shell cap comprises, for example, a thermoplastic material, in particular a POM.